Repeated attempts have been made to develop durable prosthetic heart valves with excellent physiologic function which are free of thrombosis, infection, embolism, fibroplastic overgrowth, orifice occlusion, poppet sticking and so forth. Some of these attempts are reported in: Prosthetic Heart Valves, Lyman A. Brewer, III, M.D., editor Chas. C. Thomas Publisher, Springfield, Ill., 1969; Sauvage, L. R., Viggers, R. F., Berger, K., Roble, S. B. Sawyer, P. N., and Wood, S. J., Prosthetic replacement of the aortic valve, Chas. C. Thomas Publisher, Springfield, Ill., 1972; Spencer, F. C., Reed, E. R., Clauss, R. H., Tice, D. A., Ruppert, E. M., Cloth covered aortic and mitral valve prostheses: Experiences with 113 patients; and so forth.
That thrombosis is an interfacial or surface chemical phenomenon has been known since the beginning of the 19th Century. Reports on this phenomenon may be found in: Scudamore, C., Essay on the blood, Longman, Hurst, Rees, Orme, Brown, and Green, London 1824; Text-Book of Electricity in Medicine and Surgery, George Vivian Poore, Smith, Elder and Company, London 1876.
Approximately 20 years ago, fairly clear cut evidence became avialable that electrochemical phenomena were active in both the maintenance of vascular homeostasis and in the prevention of intravascular thrombosis (Sawyer. P. N., Pate, J. W., Bioelectric phenomena as etiologic factors in intravascular thrombosis, Surg., 34:491, 1953). Briefly stated, all mechanisms which subtract electrons from blood tend to induce thrombosis, while donation of electrons to blood tends to be antithrombogenic. This is discussed in: Sawyer, P. N., Brattain, W. H., Boddy, P. J., Electrochemicl precipitation of human blood cells and its possible relation to intravascular thrombosis: The National Acad. of Sci., 51:428, 1964; Sawyer, P. N., Wu, K. T., Wesolowski, S. A., Brattain, W. H., Boddy, P. J., Electrochemical precipitation of blood cells on metal electrodes; and aid in the selection of vascular prostheses, Nat. Acad. Sci., 53:294, 1964; and so forth.
Multiple studies have been carried out on metal tubes, wires, wires at set potential and wires permitted to come to their spontaneous potential without current flow both in vitro and in vivo. Discussions of these studies appear in: Sawyer, P. N., Brattain, W. H. Brattain, W. H., Boddy, P. J., A case for considering electrochemical criteria in the choice of materials used in vascular prostheses; Ibid 337-348; Sawyer, P. N., Srinivasan, S., Metallic and prosthetic devices as vascular wall substitudes, Biophysical criteria and methods for evaluation, Biomed. Mater. Res., 1:83, 1967; Sawyer, P. N., Wu, K. T., Wesolowski, S. A., Brattain, W. H. Boddy, P. J., Long term patency of solid wall vascular prostheses, Arch. Surg., 91:735, 1965; and so forth.
These studies show that thrombosis on prosthetic surfaces is intimately related to the spontaneous potential of the metal in prosthetic valves, and ultimately to the homogeneity of surface charge and its sign of all insulator surfaces exposed to blood. This is set forth in: Sawyer, P. N., The effect of various metal interfaces on blood and other living cells, Ann. of N.Y. Acad. of Sci., 146:49, 1968; Sawyer, P. N., Srinivasan, S., Wesolowski, S. A., Berger, K. E., Campbell, A. A., Samma, A. A., Wood, S. J., Sauvage, L. R., Development and in vivo evaluation of metals for heart valve prostheses; Trans. Amer. Soc. Artif. Int. Organs 13:124, 1967.
Gradually, an experience has evolved, with the implantation of several hundred valves in dogs and calves in the tricuspid, mitral and aortic annuli by several investigators which has provided proof that valves can be made to display an increasing antithrombogenic tendency related not only to their corrosion potential, but also to their cleanliness at the time of implantation. This is seen in: Sawyer, P. N., Srinivasan, S., Lee, M. E., Martin, J. G., Murakami, T., and Stanczewski, B., Dependence of long term function of prosthetic heart valves on their interfacial potential; Proc. of II National Conf. on Prosthetic Heart Valves, Lyman A. Brewer, III, M. D., Editor, Charles C. Thomas, Publisher, Chap. 13:198, 1969; and so forth.